Abstract

Plant respiratory burst oxidase homolog (rboh) genes appear to play crucial roles in plant development, defense reactions and hormone signaling. In this study, a total of seven rboh genes from grape were identified and characterized. Genomic structure and predicted protein sequence analysis indicated that the sequences of plant rboh genes are highly conserved. Synteny analysis demonstrated that several Vvrboh genes were found in corresponding syntenic blocks of Arabidopsis, suggesting that these genes arose before the divergence of the respective lineages. The expression pattern of Vvrboh genes in different tissues was assessed by qRT-PCR and two were constitutively expressed in all tissues tested. The expression profiles were similarly analyzed following exposure to various stresses and hormone treatments. It was shown that the expression levels of VvrbohA, VvrbohB and VvrbohC1 were significantly increased by salt and drought treatments. VvrbohB, VvrbohC2, and VvrbohD exhibited a dramatic up-regulation after powdery mildew (Uncinula necator (Schw.) Burr.) inoculation, while VvrbohH was down-regulated. Finally, salicylic acid treatment strongly stimulated the expression of VvrbohD and VvrbohH, while abscisic acid treatment induced the expression of VvrbohB and VvrbohH. These results demonstrate that the expression patterns of grape rboh genes exhibit diverse and complex stress-response expression signatures.

Protein alignment and domain structure of AtRbohA and the seven predicted grape respiratory burst oxidase homolog (Rboh) proteins. (A) The red shading indicates residues that are identical and the lighter shading represents positions with a lower level of conservation. EF-hand domains are indicated by the boxes. Conserved binding sites for flavin adenine dinucleotide (FAD), NADPH-ribose and NADPH-adenine are indicated with a straight line below the alignment. Histidine residues involved in heme binding are indicated by arrows. Putative transmembrane domains (TMs) are indicated by brackets above the alignment; and (B) Schematic representation of the grape Rboh proteins with their respective functional domains, showing that grape Rboh proteins are similar to Arabidopsis AtRbohA.